Back pain affects a large proportion of the population, with 4 out of 5 adults reporting back pain at some point in their life, and approximately 7% suffering from chronic non-specific effects. The direct and indirect economic effect of this pain is substantial, with estimates that it could be up to 1-2% of GDP annually. Much chronic, non-specific back pain is believed to derive from a degenerate IVD, which typically includes early degeneration of the NP of the IVD, well before pathological changes in the surrounding annulus fibrosus (AF) are evident.
The two most widely used treatments for IVD-derived back pain are spinal fusion and conservative management. In spinal fusion the pain-generating IVD is largely excised, and the surrounding vertebrae are fused together by various means, for example using a metallic cage screwed onto each. A number of studies show long-term deleterious effects of fusion on adjacent vertebrae and discs; however it is still widely viewed as the ‘gold standard’ surgical treatment. Conservative management can take many forms, and usually involves a program of stretching, physiotherapy and pain medication. Several high-quality studies have shown minimal difference in outcome between the two treatment protocols, and relatively low levels of improvement for many patients.
There has therefore long been a need for improved management of degenerate disc disease. An obvious conceptual alternative is the surgical removal of the damaged disc, and its replacement with an artificial implant, and some whole-disc implants have FDA approval and are in clinical use. However implantation requires very invasive surgical interventions. Treatments replacing only the NP are minimally invasive and are potentially a useful alternative in many cases. However, studies have shown that these NP implants are prone to fail along the original surgical access track under normal physiological loading of the spine. It is therefore likely that successful replacement of degenerate NP will only be possible if the outer structure of the disc (known as the annulus fibrosus) is conserved during NP insertion.
There is some published literature that discusses the use of high intensity focused ultrasound (HIFU) in treatment of the intervertebral disc. However these papers relate to methods of thermally necrosing nerves in the disc to reduce pain, rather than removal of the IVD NP.